Loud pop switching between active/passive

[julesb]

Hi, my rather brilliant Yamaha BB1100 showing some odd behaviour when switching between passive and active. It seem it does it loudest on the first try and then less. Almost like a build up of  static something as it does it less or not at all after the first go. No other issues in either mode. Can't trust it live though as it's a very loud pop. Any ideas what would need replacing? Thanks in advance.

[gary mac]

I think my first course of action would be to try an application of switch cleaner on the selector.

[ikay]

My old BB1100 used to do this as well. I think it's something to do with how they've wired the active/passive switch so that it also switches the battery in. There's probably a fix using a pull-down resistor (or somesuch technical gizmology) to suppress the pop but I used to just turn down the volume before switching.

[BassBus]

1 hour ago, gary mac said:

I think my first course of action would be to try an application of switch cleaner on the selector.

...and all over the circuit board and in the pots as well.

[obbm]

It's caused by current rushing in and charging up the capacitors in the pre-amp as it powers up.  Exactly the same reason why Neutrik Silent jacks are not recommended for active instruments. 

[julesb]

Thanks all

[dyerseve]

9 hours ago, gary mac said:

I think my first course of action would be to try an application of switch cleaner on the selector.

And when doing this operate the switch several dozen times to make sure the cleaner gets in to the contacts of the switch and can work it's magic. 

New switches aren't that expensive do of switch cleaner doesn't work just swap out the switch. 

[Woodinblack]

As they say, clean the switch. If that doesn't work, put a resistor on the output (or input if that is unswitched) of the preamp.

The thump, if it isn't a bad switch, can be caused by the fact the output is floating around until you switch it into circuit. As there is no load holding it down, it can get quite high and is suddenly discharged by the load dragging it down. Also the input (although this is often still connected) which can be floating.